python回撥函式：

同步

def click(func,*args,**kwargs):

    func()

    print 'callback over'

​

def callback():

    time.sleep(1)

    print 'i am callback'

​

click（callback）

i am callback

callback over

非同步

import threading
 

import time

def callback(func):

    def wrapper(*args, **kwargs):

        t = threading.Thread(target=func, args=args,kwargs=kwargs)

        t.start()

    return wrapper

def click(func, *args, **kwargs):

    func(*args, **kwargs)

    print("callback maybe not end,but i need tell him that i've received his command")
 

@callback

def event(*args, **kwargs):

    time.sleep(*args, **kwargs)

    print('i am a event what you need now!')

@callback

def another_event(*args, **kwargs):

    time.sleep(*args, **kwargs)

    print('i am another event you need now!')

click(event,3)

click(another_event,6)

返回

其中，先學習@的最一般用法：

就是建立一個新的函式，來取代你想用的函式，其中新的函式前後包含你想要作的事.

from datetime import datetime

​

def record_time(func):

    """ 建立一個新的函式 """

    def new_function(*args, **kwargs):

        now = datetime.now()

        print(f'func called at {now}')

        value = func(*args, **kwargs)

        print(f'Execution time is {datetime.now()-now}')

        return value

    """ 返回這個新的函式 """

    return new_function

​

""" 裝飾符的使用 """

@record_time

def circle_area(radius):

    area = 3.14*radius**2

    print(f'Area of circle with radius {radius} is {area}')

    return area

​

circle_area(3)

該裝飾符就放在函式定義前一行，其意義等同於把 circle_area 函式更改為我們在 record_time 中所定義的新函式.

callback maybe not end,but i need tell him that i've received his command

callback maybe not end,but i need tell him that i've received his command

1213

>>> i am another event you need now!

i am a event what you need now!

>>> 

我們看回去：

import time

from multiprocessing import Process,Pool

​

# call1，call2，call3分別為3個主函式

def call1(n):

    time.sleep(n)

    print("call:", 1)

    return 1

​

def call2(n):

    time.sleep(n)

    print("call:", 2)

    return 2

​

def call3(n):

    time.sleep(n)

    print("call:", 3)

    return 3

​

def fun(n):

    # 回撥函式，表示執行完主函式後要完成的工作

    print("i'm done!, n={}".format(n))

​

​

if __name__ == "__main__":

    print('start')

    p = Pool(3)   # 建立程序池

    # 分別用非同步的方式執行主函式call，主函式引數n，以及回撥函式fun

    p.apply_async(func=call1, args=(1, ), callback=fun)

    p.apply_async(func=call2, args=(1, ), callback=fun)

    p.apply_async(func=call3, args=(1, ), callback=fun)

    p.close()

    p.join()

    print('end')

​